An overview of 3D Laser Scanning Process with Scan to BIM

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Overview

Scan to BIM Services is a process of capturing scanned data from the real site conditions in the form of 3D Model with the help of a scanner. It is useful for carrying out renovation projects, retrofit, and conversion projects. It can also extract accurate and precise construction information from as-built buildings.

It can be used as the production of comprehensive BIM Services Model, application of facility management, valuation purposes of existing structures or building can be procured easily, review of the plan that is altered or added, evaluating aspects of energy efficiency audit and creation of virtual tour of existing structures. It is based on the critical features of scanned data which includes geometry, mesh modeling, topography extraction, etc.

Use of laser scanner by contractors

Contractors
gather on-site information with the help of 3D Laser scanners of their project,
which helps them to get accurate data that can be further be used in all the
construction and planning process.

There are
multiple uses of a laser scanner for the contractors:-

It helps to check the progress of a model.

It can generate accurate as-built models from existing
buildings.

It can add any missing element or design to the model.

It works to inspect the as-builts model.

It can be
beneficial to the contractors within the construction industry as follows:-

Less rework from human error:- In certain
construction projects, there is often a need to do rework on aspects of the
model which takes a lot of time than expected and incurs more cost than estimated
while planning stage. With the advent of a 3D laser scanner, we can reduce the
need for rework before the model being built. Revit software can take existing
elements of a model and redesign it which can save costs and prevent rework.
Manipulation of 3D representation model can be done through Revit where 3D
laser scanners can fetch all the essential information about the model. Any
measurement can be gathered from the scanned data or point cloud model.

Evaluating documentation throughout the construction
process: – Scanner is not just used for capturing data from existing
building conditions or pre-built projects, but it can also be used for
documenting your project throughout any project’s lifespan. Any changes in the
model can be made quickly and tracked or can be useful to send a scan to
stakeholders of the project. It can make them track the update and keep team
ahead of schedule.

Reduction of costs and schedule: – By keeping
documentation of stages of the building model and reducing rework can reduce
the cost, which can drive an accurate and updated schedule. It can help to know
what materials are needed and determine the actual costs with laser scan
additional plug-ins to your software. The material can be manipulated and fetch
data for overall material and supply information of the project. By this,
everyone can be informed about material and supplies to accomplish any given
tasks.

High Precision Data: – It helps
to capture all the useful information and high precision data helps the point
cloud model to provide all the information necessary to complete a project. 3D
scanners can capture a single pixel and offer the ability to manipulate the
existing condition. By this technology, we don’t have to worry about human
errors. All the information captured can be needed by the contractors to get
the tasks completed effectively and efficiently.

How does Scan to BIM Work through 3D laser Scanners?

Scanning: capturing data

The laser
scanner is placed on a tripod, and the laser rotates in very high speed and
captures the surrounding site. However, the laser is not harmful to the naked
eyes.

The process
of scanning is straight forward, the laser beam captures the surface, and the
relative position between the surface and scanner is recorded as X, Y and Z values
commonly called as a ‘point.’ And an accumulation of these points creates a
precise 3d digital picture, called as a Point
Cloud Modeling. After capturing millions of points, the scanner will
capture color images, through which colored representation of the scan data is
generated.

To get
accurate and précised scanned data to a BIM Model, there are certain steps to
be taken. We can keep a check on our scanning process and make it more useful
and fruitful by understanding the requirements and maintaining an audit of the
following:

– The
purpose of the point cloud should be clear to the team before they visit the
site for scanning. This will increase the efficiency of the capturing of the
point cloud data for the project.

– When a
team reaches on-site to capture the point cloud, they must set up the scanner
and prepare it with a few inputs regarding the number of points to take for a
single scan and the density of scan.

– The
scanner captures only the visible surfaces. To get a clear 3d digital
presentation of the surroundings one will have to take multiple scans from
different directions as well as different angles. When we know the purpose of
the scan that what the particular scan will be used for in future we will be
quicker and fast while getting the 3d scan.

– We will
now have to take this data into a system. All the individual scans must be
registered into a single point cloud. We can use point cloud software to
register, review, and model the data.

– Once the
registration is completed, we can import this point cloud into the 3d modeling
software and start creating the model.

With laser
scanners and point cloud data, we can achieve the desired accuracy and speed in
our 3d models. The on-site information and the documentation work can get
easily synchronized, saving us from working on the long old trial and error
method.

We can get
our point cloud data in the following formats and then we will require
converting these formats into the listed formats to get the point cloud
imported in Revit:

Formats in
which we can receive the scanned data

Sequence of images

.fls

.e57

.las

.laz

.ptg

.ptx

.pcg

.ply

.xyz

.obj

There are
multiple softwares which can be used to convert the scanned data formats into
Revit further supported point cloud format such as:

Autodesk Recap

Cyclone

MeshLab

Edgewise

Pix4d

The Revit
supported formats of point cloud data are:

.rcp

.rcs

Process of Modeling with Point Cloud Software

– After importing, the point cloud in Revit,
the density of the cloud will play the key role; higher the density greater
will be the accuracy in geometry.

High Density Scan Data

Low Density Scan Data

Required time depends upon the scale of details we are focusing on; if
we are focusing on minute details, we will require more time for modeling the
entire project.

Once the point cloud is placed in the project (by origin to origin/by
center to center/ by shared coordinates or by last-place settings), we can
commence modeling.

The scan visible in the floor plan shows gaps in between the walls
(the scanner captures the surfaces only). So where we find the edges, we will
create ‘detailed lines’ all through the walls everywhere.

Now, we will place walls over these lines, we should practice the
model creation this way only to avoid errors and maintain accuracy.

This is because the scan generally gets deflected, the bottom and top
of the wall most of the time do not match. Therefore we create the walls
according to the bottom of the scan (TIP).

Later
on, we continue pacing elements the same way.

Revit with Recap is the oldest method of working on scans though.
Nowadays there are software like Edgewise,
ImaginIt, PointSense, etc. which generates model geometry from the point cloud
data itself, after that we have to finish this geometry with proper categories
of elements.

What is the QA/QC process and how it can be useful to
the construction industry?

After
completing the 3d model, it is recommended and required to do the thorough
quality checking of all the elements by overlaying the scan with the model and
rectify any errors or mismatches between the scan and elements.

Moving
forward with the process of QA/QC of a model, we should be well aware of the
tolerances which we have kept for modeling. The tolerances are dependent on two
factors:

Level of Detailing of the project

Density and Clarity of Scan

By
tolerances we mean, that how much leverage we will give to elements and their
accuracy while modeling and on the factors mentioned above we can decide until
what percentage we should take tolerances.

Conclusion

Point Cloud to BIM Services helps save
time in comparison to the traditional method. The construction cost can be
reduced to a certain extent as the BIM model can help to identify the pars of
the building to be worked upon in the primary design phase. We can even
generate the energy analysis and ensure the quality of the work which has to be
done on-site through these BIM models.